Comparing myopia control efficacy and corneal power changes in children wearing corneal refractive therapy (CRT) and vision shaping treatment (VST) orthokeratology lenses with smaller back optic zone diameters

• For 8–11-year-old children with low myopia, the 5.6 mm-BOZD VST lenses were significantly more effective at slowing axial elongation compared to the 5.0 mm-BOZD CRT lenses over the 12-month period. • The improved myopia control with the 5.6 mm-BOZD VST lenses may be attributed to a distinct optical effect: inducing a steeper RCRP profile and a greater summed RCRP value within the pupillary area. • Study provides insights into future OK lens parameter modifications aimed at enhancing efficacy. To compare axial length (AL) elongation and relative corneal refractive power (RCRP) changes in children wearing corneal refractive therapy (CRT) and vision shaping treatment (VST) lenses with smaller back optical zone diameters (BOZD). This retrospective study of 136 eyes from children aged 8-11 years, having myopia of −0.50 to −3.00 D, were included and fitted with two types of orthokeratology (OK) lenses: 5.0 mm-BOZD CRT and 5.6 mm-BOZD VST. The analysis detected AL at baseline, 6, and 12 months. The treatment zone size (TZS), treatment zone decentration (TZD) and RCRP parameters were obtained through analyzing the corneal topography maps obtained at baseline and after 1 year. The AL increase in the 5.6 mm-BOZD VST group was significantly slower than the 5.0 mm-BOZD CRT group (6 months: 0.09 ± 0.08 mm vs. 0.15 ± 0.10 mm; 12 months: 0.16 ± 0.14 mm vs. 0.31 ± 0.18 mm; both P < 0.001). The 5.6 mm-BOZD VST group showed a smaller 3/4X value (indicating the distance from which the RCRP profile first reaches its three-quarter peak) and a higher summed RCRP value within the pupillary region compared to the 5.0 mm-BOZD CRT group (both P < 0.05). However, the maximum RCRP value, TZS, and TZD were similar between the two groups. 5.6 mm-BOZD VST lenses provided superior myopia control efficacy compared to 5.0 mm-BOZD CRT lenses in 8–11-year-old children with low myopia, mainly through inducing a steeper RCRP profile and a greater RCRP sum value within the pupillary area.